September 16, 2020

Author

Suzanne Grant

TYPE

Passive Design

FAQ's

PART 10 - BUILDING A PASSIVE HOUSE

Here are some frequently asked questions we get and some general lessons learnt from this project that we would take into future Passive House designs and builds

1. How much did it cost?


This home cost $470,000 that includes the buildings (house, car port and garage) and structural landscaping (all retaining walls, side fencing replacing and the front brick pillars)

This is at our cost price, naturally we didn't pay a builders margin.

2. How does the cost compare if you were not building a Passive House?


We have calculated that this house cost 12% more than if it were a 'standard 6 star energy rating' home. These are the major elements of the Passive House and their budget impact

1. Heating & Cooling

  • Our Passive House (MHRV + Split System + Fireplace all supply only) = $14,300

VS

  • 6 Star house (ducted heating/cooling) = approx. $16,000-$20,000

2. Windows

  • Our Passive House (Unilux Triple Glazed) = $38,000

VS

  • 6 Star house (Double Glazed from a decent manufacturer) = approx. $40,000
  • 6 Star house (Single Glazed that will still pass the rating) = approx. $20,000


3. Airtight Wrap & Taping

  • Our Passive House (materials only) = $6,500

VS

  • 6 Star house (watergate wrap) = $600

As mentioned before airtightness is obviously a Passive House requirement, however Vapour membranes like the ProClima wrap are continuing to become more mainstream as the benefits are becoming more well known and there are issues becoming evident with traditional foil wrap.

4. Insulation

  • Our Passive House = $10,000

VS

  • 6 Star house = approx. $6,500


5.  Additional framing materials (walls and service cavities)

For our house and the way it was designed the approximate cost of additional materials needed is $7,500.

6. Labour

Approximately 4 weeks additional labour for 3 qualified carpenters is $15,000​

7. Passive House Consulting

  • Passive House Design & Certification = $11,500
  • MHRV commissioning = $700
  • Blower Door tests = $1,500 (in our case no additional hours or remedial investigations were needed which would be additional to the blower door test costs)


3. Can you hear the mechanical ventilation unit running?


The thick walls and floor of insulation plus the triple glazed windows makes the house very quiet in general so yes you can, however this is really only due to the fact that the entire house is quiet from external noise. It is dramatically quieter than a ducted heating/cooling unit in any other home, and another bonus is there is no draft blowing from the vents like you would from a standard heating/cooling ducted unit.


4. How often do you have to use heating/cooling?


In 2019 we plan to more accurately record how many days we turn on either the split system or fireplace, this past year would be a guesstimation of approximately 20 days for the split system (18 days being for cooling and 2 for heating for when we have been away) It's amazing how much general living in the house keeps it warm, for example running the oven, hot water for the shower or bath and just bodies living in the house. If the temperature for the day was forecast to be above about 27-30 degrees we would turn on the split system in the morning on 'night mode' or the lowest fan setting. There were days in the beginning where we wouldn't turn the air conditioner on to see how the house would respond, and when the house reached about 25 degrees it was getting a bit uncomfortable, this would generally be in the mid afternoon.

Another point is that because the air is very slow moving through the MHRV system if the weather cooled down at night we would open doors and windows to 'purge' the house.


5. Would you have a fireplace again?


Honestly, I think the jury is still out on this one. On one hand we definitely did use it over the winter and the fireplace is very efficient in itself. My past experiences of a Coonara is that you could comfortably sit in front of it, but the Euro Fireplace we have can let off some serious heat for such a small chamber! In the beginning I remember one day we had the fire on and a roast in the oven and I  actually had to opened a window to cool the house down because it was so warm. So on the other hand now that we have experienced a winter and how much the house retains heat I could understand why you don't need the fireplace.


6. Does it work?


It really does! I think after living in the house for a year you almost take it for granted, but then you will catch yourself either noticing something about another house your in or a hotel you stay at that you don't have to think about in your own home. Just generally coming or going in and out of the house is when you notice how comfortable the temperature is, and then knowing there is no heater or cooler on is pretty amazing.

One of the tell tale signs of it working is seeing the condensation on the windows on the outside. Honestly sometimes waking up it doesn't even look that cold outside but there will be condensation on the windows.

7. What would you do differently?



Sliding Doors instead of French Doors
We would do a lift and slide back door instead of the french doors leading to the deck. Originally we did the French doors because they could be airtight and they fit the traditional style, however they are heavy doors and having little ones around now they are not particularly user friendly.

Single Pane Window in Living Room
In the living room is the biggest window of the house, and it has a openable section which isn't really needed, I would make this one single pane of glass. Knowing what the window manufacturers are capable of in Europe does open up more possibilities of glazing to such a high standard.

Heat Pump Hot Water Unit
We didn't really do much investigating into this at the time and went with a pretty standard Hot Water unit set up, being a evacuated tube storage unit, however now knowing more about the efficienciesof the Heat Pumps would look into these more.

8. Would you do it again?


Without a doubt, couldn't go back.

9. General observations of living in a Passive House

  • No turning on or off an exhaust fan in the bathroom when having a shower, it boosts automatically when it detects and increase in humidity. Surprisingly it will also go into boost mode if I have just hung out a load of washing on the clothes horse in the laundry.
  • No remembering to turn the heater or cooler on or off when you leave or come home
  • Now having a little one living in the house, no need for temperature guides in the nursery to know how warm or cool it is, he sleeps in the same pyjamas and sleeping bag all year round.
  • If your in the kitchen and someone is at the front door no one can hear you call out 'Come In!


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